Simplify the following expression: $n = \dfrac{1}{10k} - \dfrac{1}{6k}$
Solution: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $10k$ and $6k$ $\lcm(10k, 6k) = 30k$ $ n = \dfrac{3}{3} \cdot \dfrac{1}{10k} - \dfrac{5}{5} \cdot \dfrac{1}{6k} $ $n = \dfrac{3}{30k} - \dfrac{5}{30k}$ $n = \dfrac{3 -5}{30k}$ $n = \dfrac{-2}{30k}$ Simplify the expression by dividing the numerator and denominator by 2: $n = \dfrac{-1}{15k}$